This invention relates to a machining time estimating device for schedule control in an electric discharge machining operation.
FIG. 1 is an explanatory diagram, partly as a block diagram, showing the arrangement of an electric discharge machining apparatus with a machining time estimating device which has been disclosed, for instance, by Published Unexamined Japanese patent application (OPI) No. 130130/1987. In FIG. 1, reference numeral 1 designates a machining electrode; 2, a workpiece to be machined, which is set on a machining stand 3; 4, a ball screw which is driven by a Z-axis DC servo motor 5 to move the machining electrode up and down; 6 and 7, an X-axis DC servo motor and a Y-axis DC servo motor for moving the machining stand 3 in an X-axis direction and in a Y-axis direction, respectively; 8, a DC source for applying a pulse voltage across the machining electrode 1 and the workpiece 2; 9, a switching transistor; 10, a pulse generator for applying a pulse signal to the switching transistor 9; and 11, a number of resistors forming a resistor switching unit.
Further in FIG. 1, reference numeral 13 designates a logical circuit for supplying control signals to the pulse generator 10 and the resistor switching unit 11; 14, a servo control circuit; 15, a drive circuit for the X-axis servo motor 6, the Y-axis servo motor 7 and the Z-axis servo motor 5; 16, a memory unit; 17, an input unit; and 18, a display unit.
FIG. 2 is a block diagram showing the machining time estimating device provided for the electric discharge machining apparatus shown in FIG. 1. The logical circuit 13 includes a calculating section 19 for calculating an estimated time. The calculating section 19 receives input data through the input unit 17 to be processed therein. The result of the operation in the calculating section 19 is applied to the display unit 18, and a part of the result data is stored in the memory unit 16.
An operation of the device will be described hereinunder. By the use of the input unit 17, data A.sub.1 indicating the bottom area of the machining electrode 1, data A.sub.2 indicating a machining depth, data A.sub.3 indicating an amount of reduction of the electrode, and data A.sub.4 indicating a series of machining conditions in steps from a rough-machining operation to a finish-machining operation are applied to the input unit 17.
The data A.sub.1 through A.sub.4 thus inputted are applied to the calculating section 19 where machining periods of time required for the various machining steps are calculated. The result of the calculation is applied, as data DT.sub.1, to the display unit 18 and the memory unit 16.
The conventional machining time estimating device is constructed as described above. Therefore, if the machining speed inherent in the machining conditions is corrected according to the present machining states such as an electrode configuration and machining depth, then a reference value for estimation will be lost, and accordingly it cannot be applied to other machining operations. Hence, the estimating device can calculate only ideal machining times. Furthermore, the inputting of an electrode configuration is to obtain a machining area or value; that is, it is not for the variation in machining characteristic due to the electrode configuration. In addition, in the conventional machining time estimating device, factors in machining environmental conditions such as a jet stream of machining solution are not taken into account at all. Hence, the machining time estimated by the conventional machining time estimating device is low in accuracy.